Demography and Population Dynamics of Amphibians in Desert Mountain Canyons Item Type text; Electronic Dissertation Authors Zylstra, Erin Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 04/10/2021 00:21:59 Link to Item http://hdl.handle.net/10150/628017 DEMOGRAPHY AND POPULATION DYNAMICS OF AMPHIBIANS IN DESERT MOUNTAIN CANYONS by Erin Rae Zylstra __________________________ Copyright © Erin R. Zylstra 2018 A Dissertation Submitted to the Faculty of THE SCHOOL OF NATURAL RESOURCES AND THE ENVIRONMENT In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY WITH A MAJOR IN NATURAL RESOURCES In the Graduate College THE UNIVERSITY OF ARIZONA 2018 STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of the requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permission, provided that an accurate acknowledgement of the source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: Erin R. Zylstra 3 ACKNOWLEDGMENTS This work would not have been possible without the help and support of numerous people. I am extremely thankful for each and every one of them. First, I have to thank my advisor, Bob Steidl, from whom I learned a great deal about ecology, statistics, writing, and more. Bob challenged me to pursue goals that I had assumed were out of reach, gave me the freedom to explore a wide range of questions and projects, and provided encouragement at every step along the way. I am extremely grateful for the experience and will be sad to see this chapter end. I am also thankful for all the support and thoughtful insights provided by my committee: Larissa Bailey, Dave Christianson, and Walt Piegorsch. I’m grateful to Larissa for asking challenging questions and offering her expertise in both amphibian ecology and statistics. I also greatly appreciated her encouragement and support, especially as I began to think about post-graduate pursuits. I enjoyed discussions with Dave about applications and extensions of our work to other species and environments, and I owe Walt thanks for encouraging me to pursue an M.S. in Statistics and providing statistical advice and expertise along the way. In addition to my committee, I also want to thank Ed Bedrick, Dean Billheimer, Joe Watkins, and others in the Statistics GIDP at the University of Arizona for helping me develop the quantitative skills I needed to finish the statistics degree and apply that knowledge to my dissertation research. It is not an overstatement to say that my accomplishments as a graduate student, and this project in particular, would not have happened without Don Swann. Over the years, I have been lucky to consider Don a mentor, collaborator, and friend. In many ways, this work is an extension of projects that Don initiated more than 20 years ago, and many of the questions I pursued stemmed from our ongoing discussions about frogs and aquatic resources in the Sky Island region. This kind of research is always collaborative, and I have been fortunate to work with great people, several of which will be co-authors on the published papers that result from this work. In addition to Bob and Don, Blake Hossack and Erin Muths contributed to the project in several ways, most importantly sharing their knowledge and expertise with regards to amphibian declines in the western U.S. They also helped to secure funding and provided valuable feedback on reports and earlier versions of the papers. I am very grateful to those who ventured in the field with me, as those days were often long, hot, and exhausting. In particular, I thank Patrick Brown, Bruce Weise, Ben Beal, Dave Prival, and James Borgmeyer. Many other people helped get me up to speed on all things frog-related, including Cecil Schwalbe, Mike Sredl, Kevin Bonine, Brent Sigafus, Dennis Caldwell, Kim Baker, Kris Ratzlaff, and David Hall. One of my dissertation chapters is based largely on long-term monitoring data from Saguaro National Park. It would be impossible to thank all of the people who contributed to those efforts, but several people deserve special recognition, including Mike Ward, Natasha Kline, Cecil Schwalbe, Scott Stonum, and Kara O’Brien. 4 This project was made possible by grants from the U.S. Geological Survey Amphibian Research and Monitoring Initiative, T & E, Inc, and the Tucson Herpetological Society. Funding for long-term monitoring efforts was provided by Saguaro National Park, the Western National Parks Association, and Friends of Saguaro National Park. I received additional support from The Wildlife Society, the Graduate and Professional Student Council at the University of Arizona, and a number of scholarships through the School of Natural Resources and the Environment and the College of Agriculture and Life Sciences. Finally, and most importantly, I thank my family, and my partner, Bruce. For your constant encouragement, your support, and your patience, I am forever grateful. 5 TABLE OF CONTENTS LIST OF TABLES ...............................................................................................................9 LIST OF FIGURES ...........................................................................................................10 ABSTRACT .......................................................................................................................12 CHAPTER 1 : DROUGHT-MEDIATED EXTINCTION OF AN ARID-LAND AMPHIBIAN: INSIGHTS FROM A SPATIALLY EXPLICIT DYNAMIC OCCUPANCY MODEL ................................................................................................. 14 ABSTRACT ..................................................................................................................... 14 INTRODUCTION .............................................................................................................. 15 METHODS ...................................................................................................................... 18 Study area ................................................................................................................. 18 Field surveys ............................................................................................................. 19 Occupancy model ...................................................................................................... 20 Environmental covariates ......................................................................................... 23 Site-level covariates .............................................................................................. 23 Season-level covariates ......................................................................................... 24 Survey-level covariates ......................................................................................... 25 Model implementation and inferences ...................................................................... 26 Forecasting effects of climate on metapopulation persistence ................................. 29 RESULTS ........................................................................................................................ 30 Field surveys ............................................................................................................. 30 Occupancy................................................................................................................. 31 Forecasts ................................................................................................................... 33 DISCUSSION ................................................................................................................... 33 Conclusions ............................................................................................................... 38 CHAPTER 2 : LOW SURVIVAL OF AN ARID-LAND AMPHIBIAN CONTRIBUTES TO POPULATION DECLINES ..................................................... 48 ABSTRACT ..................................................................................................................... 48 INTRODUCTION .............................................................................................................. 49 METHODS ...................................................................................................................... 51 Study area ................................................................................................................. 51 6 Field surveys ............................................................................................................. 53 Identifying individuals .............................................................................................. 54 Encounter histories ..................................................................................................